This invention relates to spherical powder particles and to the process for producing the particles which involves mechanically reducing the size of a starting material followed by high temperature processing to produce fine spherical particles. More particularly the high temperature process is a plasma process.
U.S. Pat. No. 3,909,241 to Cheney et al. relates to free flowing powders which are produced by feeding agglomerates through a high temperature plasma reactor to cause at least partial melting of the particles and collecting the particles in a cooling chamber containing a protective gaseous atmosphere where the particles are solidified.
The only commercial process for producing fine spherical particles of light metals such as aluminum, magnesium, and beryllium is by gas or water atomization. In some instances the process does not produce a high yield of spherical particles.
Therefore, a process for effeciently converting coarse, often non-spherical light metal based powder to spherical powder particles would be an advancement in the art.
In European Patent Application W08402864 published Aug. 2, 1984, there is disclosed a process for making ultra-fine powder by directing a stream of molten droplets at a repellent surface whereby the droplets are broken up and repelled and thereafter solidified as described therein. While there is a tendency for spherical particles to be formed after rebounding, it is stated that the molten portion may form elliptical shaped or elongated particles with rounded ends.